It is well known to use steam traps in order to trap or retain steam in a device or system, while permitting condensate to be removed. One specific type of steam trap is the inverted bucket-type steam trap which has been extensively utilized for controlling the flow of condensate from a steam heated unit to a condensate return line. Such traps are generally utilized to permit disposal of the condensate while at the same time minimizing loss of live steam from the steam heated unit.
Examples of steam traps are shown in U.S. Pat. Nos. 3,892,256, 4,096,876 and 4,149,557, all issued to the assignee of the present invention.
In conventional systems, as steam transfers its heat energy to a load, it condenses. A steam trap discharges the condensate, while retaining the steam within the system. However, as the steam trap wears out, it increasingly loses steam and wastes energy.
An inverted bucket steam trap fails when the valve therein leaks more condensate than is coming into the trap. When this occurs, the condensate level in the trap bucket is pushed down by the incoming steam until there is no longer any condensate inside the trap's bucket. The steam flows out under the bottom edge of the bucket and up through the space between the bucket and the adjacent wall of the trap casing, carrying part of the trap's condensate prime with it. This results in a loss of prime in the trap and in passage of live steam through the trap, namely undesirable steam loss by the trap.
Various device to monitor the condition of steam traps are known. These include visual monitoring of the discharge from the trap, monitoring of temperatures upstream and downstream of the trap and monitoring sounds emitted from the trap. These, as discussed in the opening remarks of U.S. Pat. No. 4,468,962, have not been entirely satisfactory. Further examples of steam trap monitoring devices include those which monitor flow upstream of the trap, such as devices disclosed in U.S. Pat. Nos. 4,305,548, 4,456,173 and 4,468,962 assigned to the assignee of the present invention. These involve placement of a vessel upstream from the steam trap in which vessel stream and condensate are separated and steam flow is monitored. These devices have operated satisfactorily but require installation of a separate vessel in the steam line upstream from the trap, involving extra equipment, installation costs and space requirements.
U.K. Pat. No. 2 022 846 and U.K. Application No. 2122 002 disclose apparatus for monitoring steam loss in a steam trap wherein, again, a separate vessel is placed upstream of the steam trap with provision for separating steam and condensate flow. In this instance, a probe located in the vessel includes an electrode located below the normal level of condensate in the vessel such that electric current can flow through the electrode, condensate and the conductive wall of the vessel. A single baffle between the inlet and outlet in that part of the vessel in which condensate can collect is perforated above the normal level of condensate in the vessel with a small steam escape hole. Excessive steam flow through the vessel results in a fall of the level of condensate on the inlet side of the baffle, at which the probe is located, and drops the level of condensate below the electrode of the probe. Since the electrode is otherwise electrically insulated from the wall of the vessel, electric current flow no longer takes place through the electrode, signaling an excessive flow of steam through the vessel and thereby indicating excessive steam loss from the trap downstream thereof and hence a faulty trap. However, since this system requires location of a separate vessel upstream of the steam trap, it involves extra equipment costs (for the vessel), installation labor and space along the steam line upstream of the trap. Moreover, this system monitors trap operation only indirectly, and not by measurement of actual steam flow, but rather by a secondary consideration, namely disturbance of condensate level in a vessel located upstream from the steam trap. Moreover, the level of condensate at the probe may change erratically as bubbles of vapor attempt to bypass the baffle by moving down through the condensate, which may produce an erratic on/off behavior in current flow through the probe in a manner not precisely representative of steam/condensate conditions in the steam trap downstream therefrom. Also, trap capacity and distance between the vessel and trap being checked can produce erratic on/off behavior in a manner not representative of the steam/condensate condition in the steam trap downstream therefrom.
Accordingly, the objects of the present invention include provision of a steam trap checker capable of checking the condition and performance of steam traps, and particularly inverted bucket steam traps; an apparatus as aforesaid in which a monitoring probe is inserted directly into the steam trap housing and which avoids any need for insertion of apparatus into the steam line upstream of the trap; an apparatus as aforesaid in which the structure added to the trap is compact and interferes neither with internal operation of the trap nor to any significant extent with space requirements outside the trap; an apparatus as aforesaid which can be added to existing stream traps in use in the field as well as being capable of incorporation into steam traps during manufacture; an apparatus as aforesaid which monitors steam trap internal operation directly by location of a probe directly within the steam trap in a predetermined relation to the normal steam/condensate interface within the trap such that internal conditions affecting operating parts of the steam trap also simultaneously and directly affect the probe as well; an apparatus as aforesaid which is of relatively low cost and high reliability; an apparatus as aforesaid in which various steam traps in a system can be provided each with its own probe but wherein a single monitoring circuit unit can be made to serve a plurality of such probes, either by connection to such plurality of probes through a selector switch for one-at-a-time selection of such probes or by providing such monitoring circuitry as a portable unit with a quick disconnect capability for being moved from probe to probe; and an apparatus as aforesaid in which the probe is readily removable from the steam trap casing for repair or replacement, and indeed wherein the probe can be replaced by a simple plug to leave the trap fully operational with the probe removed therefrom.
Other objects and purposes of the invention will be apparent to persons familiar with apparatus of this general kind upon reading the following specification and inspecting the accompanying drawings.